Does the Top Quark embrace its Antipode?

by Christian Schwanenberger (DESY)

Tuesday 15 Oct 2024, 16:00 → 18:00 Europe/Berlin

Auditorium (DESY Hamburg)

A Search for Scalars, Pseudoscalars and tt Bound States

I will present a search for heavy pseudoscalar or scalar bosons decaying to a top quark pair (tt) in final states with one or two charged leptons, using 138 fb^-1 of proton-proton collisions at √s = 13 TeV recorded by the CMS experiment. The invariant mass of the reconstructed tt system and variables sensitive to its spin state are used to discriminate against the standard model tt background and to infer properties of spin quantum numbers. An excess of the data above the background prediction, as modeled using perturbative quantum chromodynamics (QCD) only, is observed with a significance of above five standard deviations.

I will discuss three possible hypotheses to interpret the excess which is located close to the tt production threshold: by scalar production, pseudoscalar production or by the existence of a color singlet pseudoscalar tt bound state, as predicted in a simplified model of nonrelativistic QCD. For the first two hypotheses, I will outline upper limits on the coupling of pseudoscalar or scalar bosons to top quarks in a mass range of 365-1000 GeV and relative widths of 0.5-25%. For the third scenario, I will present an extracted cross section of 7.1 pb with an uncertainty of 11%.

We invite you to attend the presentation at the DESY auditorium. We also offer a webcast:

https://desy.zoom.us/j/99616528733

Meeting ID: 996 1652 8733 
Meeting Password: 733220

2024-10-15 Physics Colloquium.mp4

DESY_ttbar_search.pdf

PAPC-poster_Schwanenberger_15Oct2024.pdf